1. Field of the Invention
The present invention relates to a transformed microorganism prepared by inserting into a zinc-tolerant microorganism a D-aminoacylase-producing gene which selectively produces D-aminoacylase alone between D-aminoacylase and L-aminoacylase, and a process for producing D-aminoacylase by utilizing the transformed microorganism.
2. Description of the Related Art
D-aminoacylase is an industrially useful enzyme for the production of D-amino acids of high optical purity, which are used for the side chains of antibiotics, peptide drugs and the like.
Chemical and Pharmaceutical Bulletin 26, 2698 (1978) discloses Pseudomonas sp. AAA6029 strain as a microorganism simultaneously producing both D-aminoacylase and L-aminoacylase.
Japanese Patent Application Laid-open No. Sho-53-59092 discloses actinomycetes, such as Streptomyces olibaceus S•6245. The use of these microorganisms results in the simultaneous production of both optical isomers of aminoacylase, D-aminoacylase and L-aminoacylase. While these organisms are capable of producing D-aminoacylase, it is necessary to separate this enzyme from its optical isomer, L-aminoacylase. Thus, laborious and costly procedures are disadvantageously required for the separation of the two.
Japanese Patent Application Laid-open No. Hei-1-5488 discloses Alcaligenes denitrificans subsp. xylosoxydans M1-4 strain as a microorganism that selectively produces D-aminoacylase alone.
If this bacterial strain is utilized, no laborious work is required for the separation of D-aminoacylase from L-aminoacylase. However, the capacity of this bacterial strain to produce D-aminoacylase is insufficient. Furthermore, the nucleotide sequence of the D-aminoacylase-producing gene is not elucidated in Japanese Patent Application Laid-open No. Hei-1-5488. Thus, this document does not describe how to modify the D-aminoacylase gene so as to improve its D-aminoacylase-producing capacity or describe the creation of a transformed bacterium with an ability to produce higher amounts of D-aminoacylase.